Sir Bernard Hogan-Howe, the Metropolitan Police commissioner, reportedly told MPs that anyone who failed a test and refused help to quit drugs should face “consequences”, such as losing their job.

Combined with “robust” policing against drug dealers, he said testing could occur among “all occupations” but in particular for those in the professions of teaching, intensive care nursing and transport.

Sir Bernard said such draconian rules, and a fear of being dismissed, would be powerful deterrents for drug users.

“We have got to plant in people’s minds something to affect the demand as well as supply,” he said during a speech to the all-party parliamentary group on cannabis and children.

“You can think of many occupations where if you were working with a colleague you would want to be sure that they were drug free.”

He said that anyone caught with drugs in their system should be offered help to stop, but those who refused assistance should suffer “consequences, which would probably be about their employment”.

But the Scotland Yard chief said employers who discovered a staff member abusing drugs would not have to turn “informant” and tell the police.

While his “refreshing” comments, reported by the Daily Mail, were welcomed by campaigners, they are likely to raise civil liberties concerns.

In the United States, random drug-testing is already accepted in sectors such as education, health, retail, financial and manufacturing. Companies say the tests not only improve safety but also help identify theft risk and improve productivity.

Sir Bernard’s comments come soon after the all-party parliamentary group on drug policy reform said all illegal drugs should be decriminalised.

The cross-party group of MPs and peers argued that the least-harmful drugs should be regulated and sold in shops, with labels detailing any risks and how to use the substances properly.

But responding to the report, Downing Street said the current approach to drugs was “the right one and is working”.

During his speech, Sir Bernard expressed concerns that parents born in the Sixties and Seventies — when cannabis was weaker — were failing to warn their children about the dangers of “super-strength” skunk.

He said the potency of cannabis had increased fivefold over the past half-century, but many parents were unaware of the damage it could do to young brains.

When Chief Constable of Merseyside, Sir Bernard was credited with adopting a zero-tolerance approach known as “Total Policing”, which included a crackdown on drug dealers.

Last night, a Metropolitan Police spokesman confirmed that the commissioner had made the speech but could not provide any further details.